Today, on International Mother Language Day, which is focused on the importance of linguistic diversity for sustainable development, it is important to remember what difference being taught in your mother tongue can make to one’s ability to learn.

Choices over the language of instruction can have a huge impact on learning outcomes

In most countries in sub-Saharan Africa, the vast majority of students, probably as many as 85%, are not taught in the language they speak at home. New evidence in the 2017/8 Global Education Monitoring Report shows that 69% of adults with five years of schooling in education systems privileging indigenous languages could read an entire sentence, compared to 41% in colonial or mixed language systems – a gap of 28 percentage points. After controlling for individual characteristics, such as age, religion and place of residence, the estimated effect on literacy outcomes was even larger at 40 percentage points.

Country examples back the story up. In Ethiopia, students began to be educated in their mother tongue in 1994. This increased the education attainment level by half a year and the probability that students would be able to read an entire sentence by 40%.

In South Africa, an apartheid-era language law had forced black South Africans in Natal province to receive two more years of education in their local language than their peers in other provinces. Although the law was intended to exclude and discriminate, it had the unexpected consequence that literacy rates were 3.5% higher in Natal.

An experimental project in north-western Cameroon to instruct in the local language instead of English in grades 1 to 3 showed that the full five years of mother-tongue instruction are needed. Students involved achieved basic literacy outcomes. However, gains were not sustained with the switch to English in grade 4, which means that early-exit models should be avoided.

How do we know if children are taught in their home language?

In the 2016 Global Education Monitoring Report we had reported an estimate that 40% of the global population are taught in a language they don’t speak at home. In reality, this estimate is difficult to make.

A background paper for our 2017/8 Report looked at population statistics, language demographics and language in education policies to look at the issue across 11 countries in South-eastern Asia. In some cases, such as in Brunei, no more than 20% of children have access to an education in their home language, while in others, such as in Cambodia and Vietnam, about 90% have that opportunity.

Distinct language variants are a major challenge in making such estimates. For instance, many distinct variants of Malay are spoken in Malaysia, and they are often seen as dialects of Standard Malay. Yet no data on population proficiency in Standard Malay are available. Moreover, many ethnic Chinese Malaysians have access to education in Mandarin Chinese at the primary level, but no data exist on whether Mandarin Chinese is their home language.

Looking at policy documents gives some insight too. A recent review of policy documents in 21 countries in eastern and southern Africa showed that most countries have introduced policies of teaching in an African language from grade 1. But policies are often not implemented due to a lack of resources or will.

Learning assessments provide some useful learning on language policy

Alternative ways to find out are asking teachers, asking parents or children in household surveys or drawing on the student background questionnaires of learning assessments. On average, one in four students in countries that took part in the TIMSS survey don’t often (or ever) speak at home the language in which they were tested.

The PISA survey shows that students from immigrant families are much more likely to speak another language at home, with two-thirds of first-generation immigrant students speaking a language at home that’s different to the one they are taught in. This means that addressing language challenges is becoming a central part of education responses to migration, which new initiatives, such as the Welcome Classes set up in Germany to receive newly immigrated children are being introduced, as the 2019 Global Education Monitoring Report will show.

The reality is that language education policies are stubborn to change

While mother tongue policies may exist on paper, this sometimes doesn’t translate to the classroom. Scanning the news gives you a flavor of the frequency of debates about the issue in different countries. The back and forths about speaking Afrikaans in South African schools are one example, as are the debates around using English in elite education in India, while the majority of the country speaks national languages. Argentinian teachers have criticized the government’s decision to suspend intercultural bilingual education programmes. Lebanon’s Minister of Education has warned against linguistic desertification. In Bolivia, by contrast, language of instruction policies have been revisited.

Recognizing the rights of minority language groups helps holding governments accountable for fulfilling these rights. At the end of last year, the American Declaration on the Rights of Indigenous Peoples gave Indigenous Peoples the right to establish educational systems based around their own languages and cultures to reflect their histories and worldviews.